A model was proposed to describe the effects of surface outgrowths on the microwave surface resistance of high Tc superconducting thin films. Calculated with experimental data the microwave surface resistance at 10 GHz for c-axis oriented YBa2Cu3O7 thin films with no outgrowths could be as low as 70 and 4 μΩ at 77 and 4.2 K, respectively. The effect of the orientation of the surface outgrowths on the microwave loss has been discussed.
The microstructure at the interface between YBa2Cu3O7(YBCO) thin film and (100)LaAlO3 substrate has been investigated by using transmission electron microscopy. It has been observed that two distinct microstructural features existed in the interface: (1) A thin transitional layer of Ba3Al2O6 was frequently observed and the YBCO thin film grown on it showed stacking faults. (2) Sharp interface with no transitional layer was also occasionally observed and the YBCO film grown on it was single crystalline. In rare cases, a low symmetry phase was observed near the surface of the LaAlO3 substrate, however, the distortion caused by the lattice mismatch between this phase and the YBCO did not affect the quality of the YBCO thin film.
Accurate determination of pavement service life based on time-series pavement condition data is crucial to achieve many pavement maintenance and management objectives. Although pavement condition monitoring frequency is one of the most important influencing factors used to estimate pavement service life, previous studies and applications are mainly focused on different monitoring frequencies with equal time intervals. No studies investigating the effect of pavement monitoring frequency with unequal time intervals for the determination of pavement service life have been conducted. In this study, the effects of estimating pavement service life using two pavement condition monitoring methods (equal versus unequal time intervals) under the same monitoring frequency were investigated. Two potential influencing factors, i.e., estimation methods (trend interpolation and extrapolation) and R2 of the fitted performance curve, were considered in this study. The analysis results indicate that, compared to the equal interval monitoring method at the same monitoring frequency, especially for pavement sections using the trend extrapolation method, the estimated accuracy of pavement service life was significantly improved using the unequal interval monitoring method. According to the analysis results, an optimal pavement condition monitoring method was developed and validated based on unequal interval monitoring using actual pavement condition data of I-16 in Georgia.
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